Nanostructured Carbon-Based Gas Diffusion Layers for Enhanced Fuel Cell Performance
- TDA Research, Inc., Wheat Ridge, CO (United States)
Fuel cells can efficiently convert chemical energy into electricity through electrochemical reactions. They are often considered as the ideal power source for both mobile and stationary applications due to their high-energy efficiency, high power density and low/zero emissions. However, the widespread commercialization of polymer electrolyte membrane (PEM) fuel cells is still hindered by the high cost, limited lifetime, and system performance issues caused by many of the components, including the gas diffusion layers (GDLs). In PEM fuel cells, the electrolyte membrane must be kept wet to conduct protons. If it dries out, the fuel cell will stop working. To maintain wet conditions, an external humidifier is added to the fuel system and the fuel cell is run at 100% relative humidity (RH). In order to operate at the high RH, a conventional GDL is designed to by very hydrophobic. This allows the GDL to remove the water that is produced by the oxidation of hydrogen. The hydrophobic GDL removes water from the catalyst layer (CL) to prevent flooding which blocks the pores. This allows the gasses to reach the CL. An even greater problem is the system complexity that comes from the need to operate at high RH. Depending on the system design, the air and hydrogen feeds to the PEM fuel cell are humidified using water from a reservoir and exhaust gas recirculation. An external humidifier adds substantial complexity, volume, weight and cost to the FC system. Automobile manufacturers would prefer to eliminate the external humidifier but running the FC under low humidity causes the membrane to dry out and the FC to stop working. The major result of this Phase I SBIR project was that we demonstrated that by adding a hydrophilic layer to the GDL on the cathode side, the water generated by the oxidation of the hydrogen fuel is retained, membrane stays wet, and the PEM fuel cell can be run without the need for a humidifier. To demonstrate the long-term stability of our material, we did a 100 hour test under low RH conditions. The TDA material showed no loss in output throughout the 100 hour test. In contrast, a fuel cell using a commercial GDL sample stopped working within a few hours. Although the cost savings of running at low RH would be substantial, it only makes sense if there is no loss in fuel cell performance. We found that our material performs as well when run at low RH conditions as conventional GDLs do when operated at high RH. The key difference between our GDLs and current GDLs is our use of a unique carbon that we have developed at TDA. We have demonstrated that our nanostructured hydrophilic carbons are a much improved alternative to carbon blacks currently used as the MPL for GDLs. In Phase I, we optimized the physical properties (e.g., electrical conductivity and pore size distribution) of the new materials. We demonstrated the feasibility of the concept by ex-situ corrosion testing as well as by measuring the electrical conductivity and mass transport properties. We carried out in-situ testing by preparing complete membrane electrode assemblies and testing them under realistic fuel-cell operating conditions. We carried out a preliminary cost analysis of the materials and found that the removal of the external humidifier would result in considerable cost saving in materials, reduced parasitic losses, higher efficiency, greater reliability, as well as weight and volume reductions. We have successfully demonstrated that our new MPL material is stable and it shows outstanding performance, especially when used under low RH conditions. By using our materials, automobile manufacturers could greatly reduce the cost and complexity of fuel cell powered cars. In conclusion, we believe that we have demonstrated the technical and commercial feasibility of our MPL materials and we have shown that further funding for their development is justified.
- Research Organization:
- TDA Research, Inc., Wheat Ridge, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0018506
- OSTI ID:
- 1491584
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- TDA-2101-016-F; TDA-2101-016-F
- Country of Publication:
- United States
- Language:
- English
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